Commonly, electrical devices that process signals have an AGC circuit to reduce and prevent inter-modulation and saturation occurring in an amplification stage. In particular, an AGC circuit in a reception apparatus for a wireless communication system is used to obtain a signal having a desired level after receiving a signal having an inconstant level. The AGC circuit prevents signal saturation by decreasing a gain value when strength of an input signal is greater than or equal to a reference value, and outputs a signal having a predetermined strength by increasing the gain value when strength of the input signal is less than the reference value.
The conventional AGC circuit adjusts a power gain of a received signal so that an average power for a signal received for a particular period may remain at a predetermined target value. Generally, the average power for a received signal is represented by a Received Signal Strength Indicator (RSSI). Here, the predetermined target value becomes a target RSSI.
As described above, the conventional wireless communication system maintains the target RSSI at a predetermined level by means of the AGC circuit irrespective of the channel environment between a transmitter and a receiver.
For these reasons, in the channel environment for wireless communication where high-power interference signals are received as a received signal, quantization error may increase as an AGC operation is performed on the entire received signal including the interference signals based on the fixed target RSSI. The increase in quantization error causes performance degradation of the wireless communication system. Therefore, in the wireless environment where interference signals are present, the wireless communication system needs to provide an AGC method and apparatus for reducing quantization error that may occur for a received signal due to the interference signals.